| Project/Area Number |
17560011
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied materials science/Crystal engineering
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| Research Institution | Osaka City University |
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Principal Investigator |
MIZOGUCHI Kohji Osaka City University, Graduate School of Engineering, Associate Professor, 大学院工学研究科, 助教授 (10202342)
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| Project Period (FY) |
2005 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2005: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Keywords | coherent phonon / excitonic quantum beat / terahertz radiation / multiple quantum well / テラヘルツ電磁波発生 / 電場制御 / 量子井戸 |
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| Research Abstract |
In order to control the coupling of coherent LO phonons and quantum interferences between various excitonic states under electric fields, we have investigated the enhancement of coherent longitudinal optical (LO) phonons in multiple quantum wells (MQWs) by applying electric fields, and characterized the terahertz radiation from the enhanced coherent LO phonon and the coupled mode between excitonic quantum beat and coherent LO phonon.
We show the research results as follows.
(1) We have investigated the characteristic of the coupled mode between the excitonic quantum beat and coherent LO phonon in GaAs/AlAs MQWs under the electric field by using time-resolved pump-probe techniques. When the electric field is increased, the frequencies of the excitonic quantum beats between the light-hole exciton with n=1 (LH1 exciton) and the heavy-hole exciton with n=1 (HH1 exciton), and between the HH1 exciton and the HH2 exciton are shifted to the higher frequency side, where n indicates the quantum number of the exciton state confined in the quantum well. Moreover, as the frequency of the excitonic quantum beat approaches that of the coherent GaAs-like LO phonon, the oscillation amplitude of the coherent GaAs-like LO phonon is enhanced due to the coupling of the excitonic quantum beat to the coherent LO phonon through the longitudinal polarization.
(2) We have investigated the terahertz radiation from the GaAs/AlAs MQWs under the electric field. The intense terahertz radiation from the coherent LO phonon was observed in the GaAs/AlAs MQWs under the electric field, while that from the excitonic quantum beat was not observed in the present samples. We found that the intensity of the terahertz radiation from the coherent LO phonon is resonantly enhanced, when the energy difference between the HH2 and HH1 excitons in GaAs/AlAs MQWs by applying the electric field becomes close to the energy of the coherent GaAs-like LO phonon.
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